Re: boot environment and /var/db/etcupdate ?

On 2022-Aug-23 15:52:53 -0700, John Kennedy <warlock@phouka.net> wrote:
>On Tue, Aug 23, 2022 at 04:02:48PM +0200, Ronald Klop wrote:
>> Hi,
>> 
>> I'm running the super duper boot environment using ZFS. [1]
>> 
>> I have /var and /usr/local as separate datasets. These do not change when I upgrade the OS and that keeps the backups a lot smaller as the backup sees a new BE as a new dataset and fully zfs sends all the data again.
>> 
>> But when I rollback /var/db/etcupdate is not in sync with / anymore.
>> And /var/db/ports and /var/db/pkg should be kept in sync with /usr/local. But I do not need to rollback these if I need to go back to the previous BE.

Looking in /var, the only thing I can see that needs to track the BE
is /var/db/etcupdate - everything else should preferentially be
outside the BE (and having things like e.g. /var/mail in the BE will
cause problems if you rollback the BE).

/usr/local and /var/db/pkg need to track to prevent package installation
metadata getting out of step with the actual installed packages.

>  For my part, /var/db/pkg is mostly just a reference to my local
>poudriere package stash and is relevant to the BE (but pretty stagnant
>unless I'm changing major versions between 12/13/14).  On my system,
>/var/db is part of /.

Several database ports default to putting their data under /var/db so
having that in a BE is likely to cause problems if you rollback.

>  I'd be a little leery of having /usr/local decoupled from the BE,
>but that's mostly worried about things like kernel drivers that would
>get out of sync with the kernel in the BE.

Kernel driver ports should all be in /boot/modules, not /usr/local (this
does mean that rolling back a BE will cause problems with the metadata
associated with those ports, but typically there are relatively few
such ports).  I don't believe there are any other ports that are
tightly bound to the actual running kernel (though sysutils/lsof comes
close).

A downside of putting /usr/local in the BE is that another large
collection of ports default to storing their data under /usr/local
and that should be decoupled from BEs.

Overall, I don't believe there's a one-size-fits-all solution to
identifying what should be part of the BE.  If you are using BEs
to switch between major versions, it probably does make sense to
include /usr/local in the BE - but then you need to extricate all
the application data that needs to not be rolled back.

-- 
Peter Jeremy